Fix incorrect typecast.
Fix incorrect typecast.

Ashutosh Sharma, per a report from Mithun Cy.

Discussion: 8544a3c34fe9ff4d29b06fb6559fed2b73f45487@mail.gmail.com

adam8157/gpdb,adam8157/gpdb,greenplum-db/gpdb,xinzweb/gpdb,greenplum-db/gpdb,lisakowen/gpdb,adam8157/gpdb,adam8157/gpdb,adam8157/gpdb,50wu/gpdb,xinzweb/gpdb,lisakowen/gpdb,lisakowen/gpdb,greenplum-db/gpdb,adam8157/gpdb,greenplum-db/gpdb,greenplum-db/gpdb,xinzweb/gpdb,50wu/gpdb,xinzweb/gpdb,greenplum-db/gpdb,50wu/gpdb,lisakowen/gpdb,adam8157/gpdb,xinzweb/gpdb,50wu/gpdb,50wu/gpdb,50wu/gpdb,greenplum-db/gpdb,adam8157/gpdb,xinzweb/gpdb,xinzweb/gpdb,lisakowen/gpdb,50wu/gpdb,lisakowen/gpdb,lisakowen/gpdb,greenplum-db/gpdb,xinzweb/gpdb,50wu/gpdb,lisakowen/gpdb